Add missing F32->I64 vec_signede, F32->I64 vec_signedo, F32->U64 vec_unsignede, and F32->U64 vec_unsignedo to altivec.h header

[johnplatts]

GCC 15 has removed the __builtin_vsx_xvcvspsxds builtin and replaced the __builtin_vsx_xvcvspsxds builtin with F32->I64 vec_signede/vec_signedo intrinsics.

GCC 15 has also removed the __builtin_vsx_xvcvspuxds builtin and replaced the __builtin_vsx_xvcvspuxds builtin with F32->U64 vec_unsignede/vec_unsignedo intrinsics.

Clang already has the F64->I32 vec_signede/vec_signedo and F64->U32 vec_unsignede/vec_unsignedo intrinsics, but not the F32->I64 vec_signede/vec_signedo or the F32->U64 vec_unsignede/vec_unsignedo intrinsics.

The following functions need to be added to clang/lib/Headers/altivec.h:

• vector signed long long vec_signede(vector float a): equivalent to __builtin_vsx_xvcvspsxds on big-endian VSX and equivalent to __builtin_vsx_xvcvspsxds(vec_sld(a, a, 4)) on little-endian VSX
• vector signed long long vec_signedo(vector float a): equivalent to __builtin_vsx_xvcvspsxds on little-endian VSX and equivalent to __builtin_vsx_xvcvspsxds(vec_sld(a, a, 4)) on big-endian VSX
• vector unsigned long long vec_unsignede(vector float a): equivalent to __builtin_vsx_xvcvspuxds on big-endian VSX and equivalent to __builtin_vsx_xvcvspuxds(vec_sld(a, a, 4)) on little-endian VSX
• vector unsigned long long vec_unsignedo(vector float a): equivalent to __builtin_vsx_xvcvspuxds on little-endian VSX and equivalent to __builtin_vsx_xvcvspuxds(vec_sld(a, a, 4)) on big-endian VSX

[johnplatts]

@nemanjai What is the status of the addition of the missing VSX intrinsics described in this issue (which were recently added to the upcoming GCC 15 release) to Clang's version of altivec.h?

[nemanjai]

@lei137 Do you know if there are any plans to add this?
@johnplatts are you interested in opening a pull request to add these?